Acute focal cerebral ischemia (stroke) is the cause of significant mental and physical disability; the susceptible age group represents an increasingly larger proportion of the U.S. population. Currently, treatment for stroke focuses upon rehabilitation; however, many stroke patients are left with extensive residual impairment. In 1966, Heyman and Saltzman reported that hyperbaric oxygenation (HBO) produced a remission of focal neurological signs and symptoms in some acute stroke patients; however, symptoms of old stroke were unaffected by such therapy. Since then a number of other investigators have reported similar findings with HBO in uncontrolled clinical studies. We propose to study the effects of HBO on the behavioral and physiologic characteristics of acute stroke patients in comparison with findings in a control group of patients treated with more conservative approaches. We will apply numerically scaled neurological and neuropsychological measures, and non-invasive regional cerebral blood flow and invasive cerebral blood flow and metabolic measures to evaluate our patients, and to assess the acute and long-term effects of HBO therapy as compared with usual methods. As the results of these studies, we hope to measure the benefit from use of HBO in the treatment of acute stroke; develop an efficient diagnostic procedure to determine which acute stroke patients may benefit from HBO; and determine optimal HBO dosage schedules.